Author: Mr Lafferty@mathsrevision.com
Date: 2 April 2013

$ m _1×m_2 $

m_1 = 1 (slider from -5 to 5, step 0.1)
C_1 = 0 (slider from -5 to 5, step 1)
m_2 = -1 (slider from -5 to 5, step 1)
C_2 = 0 (slider from -5 to 5, step 1)
A: y = m_1 * x + C_1
B: y = m_2 * x + C_2
α = Angle(A, B)
text1: "$ y=" + (LaTeX[m_1]) + "x+" + (LaTeX[C_1]) + " $"
text2: "$ y=" + (LaTeX[m_2]) + "x+" + (LaTeX[C_2]) + " $"
text3: "$= " + (LaTeX[m_1]) + "×" + (LaTeX[m_2]) + "$"
m: m_1 * m_2
text5: "=" + (LaTeX[m]) + ""
"=" + m + "": "=" + (LaTeX[m]) + ""